Observations of correlated behaviour of stratospheric ozone and aerosol at Thule during winter 1991-1992

A lidar has been installed in Thule, Greenland, by the University of Rome in the fall of 1990. Intensive series of aerosol measurements have been carried out in the period early December 1991 – early March 1992, in the context of the European Arctic Stratospheric Ozone Experiment (EASOE). In the same period, several ozonesondes have been launched by the Danish Meteorological Institute. The arctic stratosphere appears loaded with aerosol following the Mt. Pinatubo eruption of June 1991. Scattering ratios as high as 5 have been observed. Both the aerosol and ozone profiles display a layered structure, with a large variability: the aerosol and ozone contents in the layers frequently appear to be negatively correlated, particularly in the height region around 16 km. Fluctuations of the ozone content as high as 50% of the average value have been observed in levels where aerosol layers are present. These results bear a relation to those obtained in past studies of the Mount Agung and El Chichón eruptions, and in observations of Polar Stratospheric Clouds obtained at South Pole.